Golf club and method for adjusting characteristics of the same

ABSTRACT

A golf club includes: a shaft; a head; and a shaft case, and a hosel column wherein: a threaded ring including a plurality of threads provided on an inner periphery of an inner hole of the threaded ring is provided on an upper side of a dividing member, the threads extending in an axis center direction of the inner hole; the shaft case includes a convex axis member provided at a top end of the shaft case; the convex axis member is inserted in the inner hole of the threaded ring, and any one of corner edges of the convex axis member and the convex threads connect with the threads of the threaded ring; and a bolt that is inserted into a bolt insertion hole provided to the dividing member from a sole side of the head is screwed into the shaft case.

BACKGROUND

1. Field of the Invention

The present invention relates to golf clubs, and in particular, relates to a golf club of which characteristics such as a lie angle, a slice angle, and a progression can be easily adjusted. In addition, the present invention relates to methods for adjusting the characteristics of the golf club.

2. Description of the Related Art

A golf club includes a shaft, and a head attached to a top end portion of the shaft. A grip is attached to a base end portion of the shaft.

A conventional general golf club head includes a hosel hole that is directly provided to the head, and a shaft is inserted into and bonded to the hosel hole with an adhesive agent. An epoxide-based adhesive agent is generally used for the adhesive agent. In making a shaft change, the hosel portion is heated to destroy the structure made from the cured epoxy resin, and thereby the shaft can be pulled out of the hosel hole.

The conventional general golf club head having this configuration has a lot of trouble in making a shaft change. In addition, characteristics such as a lie angle, a slice angle, and a progression of the golf club head cannot be adjusted.

JP-A-2012-165864 describes a golf club that allows a shaft change to be easily made, and of which characteristics such as a lie angle, a slice angle, and a progression can be adjusted, and describes a method for adjusting the characteristics of the golf club. The golf club head of JP-A-2012-165864 has a configuration such that a head is attached to the top end of a shaft, where the top end of the shaft is inserted into and bonded to a shaft insertion hole of a shaft case, the shaft case is inserted into a shaft case insertion hole of a hosel column of the head, and the shaft case is fixed insertable and removable to the hosel column by a bolt inserted from a sole side of the head.

In the golf club of JP-A-2012-165864, putting or removing the bolt allows the shaft case to be fixed to or pulled out of a hosel mounting hole. Thus, the phase of a circumferential direction of the shaft case is changed, and the shaft case is attached again to the shaft case with the bolt.

Thus, when the axis center of the shaft is oblique to the axis center of a hosel insertion hole, changing the phase of the circumferential direction of the shaft case can adjust only a lie angle or a slice angle in the golf club having the identical shaft and the identical head main body.

In addition, in the case of a shaft case having a configuration such that an axis center position of an insertion hole of the shaft case is decentered in a parallel translation manner from an axis center position of a hosel, changing the phase of a circumferential direction of the shaft case allows a progression and the distance between a shaft and the center of gravity (the center of gravity distance) to be adjusted in the golf club having the identical shaft and the identical head main body.

Further, In JP-A-2012-165864, a shaft case of a pattern identical to the shaft case is prepared as a shaft case, and a shaft with other characteristics is bonded to the prepared shaft case to prepare a shaft case-shaft connected body, and by replacing the previously-used shaft case-shaft connected body with the prepared shaft case-shaft connected body to attach to the hosel of the head, the golf club that is different only in shaft can be obtained.

A similar golf club is described also in JP-A-2006-42951.

In the golf club of JP-A-2012-165864, a spacer that includes a pyramid-shaped hole is used in order to prevent rotation of a shaft case. In the golf club of JP-A-2006-42951, an inner periphery in the deepest recess of an inner hole of a hosel hole is processed to have a regular hexagonal shape, and a top end portion of a shaft case is processed to have a hexagonal shape, and thereby the shaft case is prevented from rotating.

In the golf club of JP-A-2012-165864 described above, because the spacer that includes the pyramid-shaped hole is used in order to prevent rotation of the shaft case, highly precision processing is required, which causes an increase in cost.

In the golf club of JP-A-2006-42951, because the inner periphery in the deepest recess of the inner hole of the hosel hole is processed so as to have a regular hexagonal shape, highly precision processing is required, which causes an increase in cost.

SUMMARY

An object of the present invention is to provide a golf club that allows a shaft change to be easily made, of which characteristics such as a lie angle, a slice angle, and a progression can be adjusted, and that is lower in production cost than the golf clubs of JP-A-2012-165864 and JP-A-2006-42951, and to provide a method for adjusting the characteristics of the golf club.

According to a first aspect of the invention, there is provided a golf club including: a shaft; a head attached to a top end of the shaft; and a shaft case having an approximately cylindrical shape, bonded to the top end of the shaft, inserted into a hosel column of the head, and fixed to the hosel column, wherein: the hosel column includes a dividing member; a threaded ring including a plurality of threads provided on an inner periphery of an inner hole of the threaded ring is provided on an upper side of the dividing member, the threads extending in an axis center direction of the inner hole; the shaft case includes a convex axis member provided at a top end of the shaft case; the convex axis member has a prism shape, or includes convex threads that extend in an axis center direction on an outer periphery of the convex axis member; the convex axis member is inserted in the inner hole of the threaded ring, and any one of corner edges of the convex axis member and the convex threads connect with the threads of the threaded ring; and a bolt that is inserted into a bolt insertion hole provided to the dividing member from a sole side of the head is screwed into the shaft case, whereby the shaft case is fixed to the hosel column.

The convex axis member may include a female screw hole on a top end face of the convex axis member, and the bolt may be screwed into the female screw hole.

An axis center of the shaft may be in a slanting direction with respect to an axis center of the cylindrical-shaped shaft case.

The axis center of the shaft may be parallel to an axis center of the cylindrical-shaped shaft case.

The threads of the threaded ring may include threads that have different depths from an upper end of the ring.

According to a second aspect of the invention, there is provided a method for adjusting characteristics of the golf club according to any one of the above, the method including: unbolting the bolt to disengage the convex axis member of the shaft case from the threaded ring; rotating the shaft case, and then connecting the convex axis member of the shaft case with the threaded ring; and fixing the convex axis member of the shaft case to the threaded ring with the bolt.

According to a third aspect of the invention, there is provided a method for replacing the shaft of the golf club according to any one of the above with another shaft to adjust characteristics of the golf club, the method including: bonding in advance the another shaft to another shaft case to produce another shaft case-shaft connected body; removing the shaft case-shaft connected body that is attached to the golf club from the head; and attaching the other shaft case-shaft connected body to the head.

In the golf club according to the present invention, the shaft case is inserted in the hosel column, and is fixed by the bolt that is inserted from the sole side. In the golf club according to the present invention, the threaded ring is provided on the upper side of the dividing member provided inside of the hosel column. Because the corner edges or the convex threads of the convex axis member provided at the top end portion of the shaft case connect with the threads of the inner hole of the threaded ring, positioning in a circumferential direction of the shaft case can be effected.

In the golf club according to the present invention, when the bolt is loosened and unbolted, the convex axis member of the shaft case can be pulled out of the threaded ring, and the shaft case can be rotated in the circumferential direction to have its orientation (the phase of the circumferential direction) changed. Thus, for example, when a shaft case having a configuration such that the axis center of the shaft is inclined in a slanting direction (e.g., an oblique direction) with respect to the axis center of an insertion hole of the shaft case is used, changing the phase of the circumferential direction of the shaft case changes an attaching direction of the shaft with respect to a head main body, and thereby a lie angle and a slice angle are changed. Thus, only the lie angle and the slice angle can be adjusted in the golf club having the identical shaft and the identical head main body.

In addition, when a shaft case having a shape such that an axis center position of an insertion hole of the shaft case is displaced in a parallel translation manner from an axis center position of a hosel insertion hole is used, changing the phase of a circumferential direction of the shaft case allows a progression and the distance between the shaft and the center of gravity (the center of gravity distance) to be adjusted in the golf club having the identical shaft and the identical head main body.

In addition, when the threaded ring including the threads that have different depths from the upper end of the ring is used as the threaded ring, changing the phase of a circumferential direction of the shaft case allows an insertion depth of shaft case into the threaded ring to be changed, which can change the entire length of the golf club.

In the present invention, a shaft case of a pattern identical to the shaft case is prepared as a shaft case, and a shaft with other characteristics is bonded to the prepared shaft case to prepare a shaft case-shaft connected body, and by replacing the previously-used shaft case-shaft connected body with the prepared shaft case-shaft connected body to attach to the hosel of the head, the golf club having the different shaft can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawing which is given by way of illustration only, and thus is not limitative of the present invention and wherein:

FIG. 1 is a front view of a head according to an embodiment of the present invention;

FIG. 2 is a side view of the head shown from a heel side;

FIG. 3 is a cross-sectional view taken along the line III-III of FIG.

FIG. 4 is an exploded perspective view of a golf club;

FIGS. 5A and 5B are cross-sectional views of a threaded ring;

FIG. 6 is a perspective view showing a method for producing the golf club (a method for welding the threaded ring);

FIG. 7 is a perspective view showing the method for producing the golf club (the method for welding the threaded ring);

FIG. 8 is a cross-sectional view showing the preferred embodiment of the present invention;

FIGS. 9A, 9B, 9C, 9D, 9E and 9F are views of a hosel column according to the preferred embodiment of the present invention showing its configuration, where FIG. 9A is a perspective front view, FIG. 9B is a front view, FIG. 9C is a cross-sectional view taken along the line C-C of FIG. 9B, FIG. 9D is a view taken in the direction of the arrow D of FIG. 9A, FIG. 9E is a view taken in the direction of the arrow E of FIG. 9A, and FIG. 9F is a back view of the hosel column;

FIG. 10 is a perspective view showing a method for producing the head;

FIG. 11 is a cross-sectional view showing another preferred embodiment of the present invention;

FIG. 12 is a perspective view of a convex axis member having another shape;

FIG. 13 is a perspective view of a convex axis member having another shape;

FIG. 14 is a perspective view of a convex axis member having another shape;

FIGS. 15A and 15B are views of a threaded ring having another structure, where FIG. 15A is a perspective view, and FIG. 15A is a cross-sectional view taken along the line B-B of FIG. 15A; and

FIG. 16 is a cross-sectional view of the golf club including the threaded ring shown in FIGS. 15A and 15B, showing the same portion as the view shown in FIG. 3

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a description of embodiments of the present invention will be provided with reference to the drawings.

FIGS. 1 to 10 show a golf club according to a first embodiment of the present invention. It is to be noted that in FIGS. 9A to 9F, a diameter/length ratio of a hosel column is shown larger than the hosel column that is shown in FIGS. 1 to 3 in order to clearly show the inclination of an inner hole of the hosel column.

This golf club has a configuration such that a shaft 4 is attached to a hosel column 3 of a head 1 via a shaft case 5, a threaded ring 8, and a bolt 7.

The head 1 is a hollow wood-type head, and includes a face portion 1 a, a crown portion 1 b, a sole portion 1 c, a toe portion 1 d, a heel portion 1 e, a back portion 1 f, and a hosel portion 1 g.

As shown in FIG. 3, the hosel portion 1 g is provided on the crown portion 1 b on the side of the face portion 1 a and on the side of the heel portion 1 e. The hosel column 3 is connected to the hosel portion 1 g, and extends toward the sole portion 1 c. The hosel column 3 has a cylindrical pipe shape, and includes a dividing member 6 provided at some midpoint in a longitudinal direction (an axis center direction) of an inner hole of the hosel column 3, the dividing member 6 being vertical to the axis center direction. The threaded ring 8 is disposed on an upper side of the dividing member 6. In addition, the shaft case 5 is inserted on the upper side than the dividing member 6. The bolt 7 is inserted from bottom up into a bolt insertion hole (opening) 6 a provided in the dividing member 6, and screwed into a female screw hole 5 m of the shaft case 5.

As shown in FIGS. 3 to 6, and FIGS. 9A to 9F, the shaft case 5 defines a cylindrical-shaped member having an outer diameter that is slightly smaller than the inner diameter of the hosel column 3, and includes an insertion hole 5 h for the shaft 4 that is provided from the upper end side to the lower end side. The shaft 4 is inserted into the insertion hole 5 h and bonded to the shaft case 5 with an adhesive agent. It is preferable that the insertion hole 5 h have a depth equal to or more than 10 mm, for example, a depth of 10 to 50 mm, and in particular, it is preferable that the insertion hole 5 h have a depth of 20 to 40 mm.

A flange member 5 b that has the shape of a guard extending outward is provided at an upper end (back end) of the shaft case 5. The flange member 5 b has the shape of an annular disk; however, it is also preferable that the flange member 5 b have a tapered shape such that the flange member 5 b is reduced in diameter more toward the top end of the flange member 5 b, while the present invention is not limited to these configurations.

A convex axis member 5 a that has a quadrangular prism shape is provided so as to project at a lower portion (top end portion) of the shaft case 5. The convex axis member 5 a shares the axis center with the outer periphery of the shaft case 5. The convex axis member 5 a is square in vertical cross section to an axis center direction of the convex axis member 5 a. It is to be noted that as shown in FIGS. 9A to 9F, a groove 5 e is provided around a base portion of the convex axis member 5 a.

A female screw hole 5 m is provided to the convex axis member 5 a so as to cave in the axis center line direction from a top end face of the convex axis member 5 a.

As shown in FIGS. 5A and 5B, the threaded ring 8 defines a ring having an outer peripheral shape of a cylinder.

The threaded ring 8 has an inner hole that has a concave polygonal shape of a dodecagon. That is, twelve concave threads 8 i are provided on an inner periphery of the threaded ring 8 so as to extend in a direction parallel to the axis center line of the threaded ring 8. The angle of a thread bottom of each concave thread 8 i is 90 degrees, and the four corner edges of the convex axis member 5 a having the quadrangular prism shape engage with the four concave threads 8 i as shown in FIG. 5B. The convex axis member 5 a is capable of engaging with the threaded ring 8 with its orientation changed in units of 30 degrees as clearly shown in FIG. 5B.

While the inner hole of the threaded ring 8 shown in FIGS. 5A and 5B has the concave polygonal shape of a dodecagon, it is also preferable that the inner hole of the threaded ring 8 have a concave polygonal shape of an octagon. In this case, the convex axis member 5 a connects together with the threaded ring while the orientation of the convex axis member 5 a is changed in units of 45 degrees.

In the present invention, it is also preferable to provide a tapered portion to the top end of the convex axis member 5 a in order to insert the convex axis member 5 a having the quadrangular prism shape more easily into the concave threads 8 i of the threaded ring. Examples of the tapered portion are shown in FIGS. 12 and 13. A convex axis member 5 a′ of a shaft case 5′ shown in FIG. 12 is provided with tapered portions 51 having a shape such that top end sides of the four thread corner edges of the convex axis member 5 a′ having the quadrangular prism shape are cut at a bevel. A convex axis member 5 a″ of a shaft case 5″ shown in FIG. 13 is provided with tapered portions 52 having a shape such that the entire circumference of a top end face of the convex axis member 5 a″ having the quadrangular prism shape is cut at a bevel.

The threaded ring 8 defines a ring-shaped member having a small axial length that is disposed only in the deepest recess of the hosel column 3, and small in weight. The threaded ring 8 is inserted into the hosel column 3, and welded to the hosel column 3. The welding method will be described later.

In order to assemble the golf club, the threaded ring 8 is disposed in the deepest recess of the hosel column 3, and welded to the hosel column 3 in advance. In addition, the shaft case 5 is bonded to the top end of the shaft 4 with an adhesive agent to prepare a shaft case-shaft connected body. It is preferable that the adhesive agent be applied onto the outer periphery at the top end portion of the shaft 4, and the shaft 4 be inserted into the deepest recess of the shaft insertion hole 5 h of the shaft case 5. An epoxide-based adhesive agent is preferably used for the adhesive agent.

It is to be noted that in the present embodiment, the female screw hole 5 m does not penetrate the shaft case 5 as shown in FIG. 3. In this case, it is preferable that a small hole for removing air with which the female screw hole 5 m and the shaft insertion hole 5 h are communicated be provided to the female screw hole 5 m so that the air passes through the female screw hole 5 m to flow out when the shaft 4 is inserted into the shaft insertion hole 5 h.

The shaft case 5 of the shaft case-shaft connected body is inserted into the hosel column 3, the convex axis member 5 a of the shaft case 5 is inserted into the inner hole of the threaded ring 8, and the corner edges of the prism of the convex axis member 5 a are engaged with the concave threads 8 i of the threaded ring 8. Then, the bolt 7 is screwed into the female screw hole 5 m through the bolt insertion hole 6 a.

Thus, the shaft case 5 is fixed to the head 1 as shown in FIGS. 1 and 3. Because the shaft case 5 is strongly bonded to the shaft 4 with the adhesive agent, the golf club having a configuration that the shaft 4 and the head 1 are of a monolithic construction is brought to completion. Because the corner edges of the shaft case 5 are engaged with the concave threads 8 i of the threaded ring 8, the phase of a circumferential direction of the shaft 4 and the shaft case 5 is precisely determined. In addition, the shaft 4 and the shaft case 5 possess high fixation stiffness in a torque direction.

In the present invention, a shaft change in the golf club can be made easily. In making a shaft change, a shaft case of a pattern identical to the shaft case 5 is bonded in advance with an adhesive agent to a new shaft to be replaced with.

By unbolting the bolt 7 of the existing golf club, the existing shaft 4 is removed together with the existing shaft case 5 from the head 1. Then, the new shaft attached with the shaft case (the shaft case-shaft connected body) is inserted into the head 1 to be fixed by the bolt 7.

As described above, the shaft attachment and the shaft change can be made very easily and promptly. In making a shaft change in a conventional golf club, a hosel portion of the existing golf club is heated to destroy a structure made from a cured adhesive agent to pull the shaft out of the hosel hole, and a new shaft is bonded with an adhesive agent, so that it takes a few hours to one day; however, in the above-described embodiment of the present invention, the shaft case 5 is attached in advance to the new shaft with the adhesive agent, so that the shaft change can be made within a few minutes. Thus, by preparing shafts of a variety of specifications that are attached with shaft cases, a method for using a golf club to make trial shots by attaching different shafts one by one to the identical head 1 can be achieved.

In the present embodiment, the axis center of the shaft insertion hole 5 h is oblique to the axis center of the outer periphery of the shaft case 5, that is, the axis center of the hosel column 3 as shown in FIGS. 8 and 9A to 9F, so that the inclination of the shaft 4 is changeable. To be specific, an axis center line a₁ of the outer periphery of the shaft case 5 is oblique with respect to an axis center line a₂ of the shaft insertion hole 5 h at an angle θ as shown in FIG. 9C. In the usual case, the angle θ is preferably about 0.1 to 5 degrees, and more preferably about 0.25 to 3 degrees.

It is to be noted that the axis center lines do not have to intersect each other, and may have a “twisted” relation. That is, the axis center lines may have a relation such that the axis center lines do not intersect each other while one of the axis center lines passes through the vicinity of the other axis center line.

As shown in FIG. 9A, a mark “N” that indicates a neutral position is provided on an outer periphery of the flange member 5 b of the shaft case 5 at a position where a plane including the axis center line a₁ and the axis center line a₂ intersects with the outer periphery of the flange member 5 b, the position being opposite to the axis center line a₂ across the axis center line a₁. In addition, a mark “NEUTRAL” that indicates a neutral position is provided on a lower side (a side close to the convex axis member 5 a) of the mark “N”. Marks “R” and “RIGHT” are provided to the left side at 90 degrees of the marks “N” and “NEUTRAL”, marks “L” and “LEFT” are provided to the right side at 90 degrees of the marks “N” and “NEUTRAL”, and marks “U” and “UPRIGHT” are provided to the opposite side at 180 degrees of the marks “N” and “NEUTRAL”. Each of the marks “NEUTRAL”, “RIGHT”, “LEFT”, and “UPRIGHT” extends in a direction parallel to the axis center line.

In FIGS. 1 to 3, the marks “N” and “NEUTRAL” of the shaft case 5 face the toe side. This state defines a normal state of this golf club.

In contrast, the shaft case shown in FIG. 8 is rotated 90 degrees in a clockwise direction in a plan view from the state shown in FIGS. 1 to 3, and the marks “L” and “LEFT” face the toe side. That is, the “L” side shown in FIG. 9F faces the toe side. Thus, the axis center line of the shaft 4 is inclined toward the face side with respect to the axis center line of the hosel column 3 in FIG. 8. Rotating the shaft case 5 90 degrees or 180 degrees from the state shown in FIG. 8 allows the inclination direction of the shaft 4 to be changed. To be specific, the shaft 4 can be inclined to the toe side or the back side.

Changing the inclination direction of the shaft 4 in this manner changes a lie angle and a slice angle.

A description of the lie angle is provided. By making the marks “N” and “NEUTRAL” face the toe side, the lie angle is smallest when the shaft 4 is inclined most to the heel side, and defines the flattest lie angle. When the marks “U” and “UPRIGHT” are made to face the toe side, that is, when the face shown in FIG. 9E is made to face the toe side, the lie angle defines the most upright lie angle.

A description of the slice angle is provided. The state where the face shown in FIG. 9B (N, NEUTRAL) faces the toe side defines a normal state. In FIG. 8 where the shaft 4 is most inclined to the face side by making the marks “L” and “LEFT” face the toe side, the face is in a hook face state where the face is most closed. In contrast, by making the marks “R” and “RIGHT” face the toe side to incline the shaft 4 most in a rear direction, the face is in a slice face state where the face is most open.

As described above, using the shaft case 5 shown in FIGS. 9A to 9F allows the inclination direction of the shaft 4 with respect the head 1 to be changed, which allows the lie angle and the slice angle to be changed. In the above description, the orientation of the shaft case 5 is changed in units of 90 degrees; however, the orientation of the shaft case 5 may be changed in units of 30 degrees or 45 degrees. Thus, the golf club can be brought into intermediate states between the above-described states. The specification of the golf club can be finely adjusted to be, for example, “slightly hook face”, “slightly slice face”, or “slightly upright lie angle”.

A shaft case 5A shown in FIG. 11 has a shaft insertion hole 5 h that is decentered from an axis center position of the shaft case 5. The axis center of the shaft insertion hole 5 h is parallel to the axis center of the outer periphery of the shaft case 5, and is slightly apart (e.g., 0.5 to 4 mm apart) from the axis center.

Using the shaft case 5A can adjust the progression of the shaft. For example, it is possible to bring the shaft 4 closer to the face side than the shaft 4 shown in FIG. 3 by the eccentric distance.

It is possible to change the position of the shaft 4 in a parallel translation manner from the state shown in FIG. 11 to the heel side, back side, or the toe side by pulling the shaft case 5A once from the hosel column 3 by unbolting the bolt 7, and rotating the shaft 4 90 degrees, 180 degrees, or 270 degrees. Changing the position of the shaft 4 in this manner allows the distance between the axis center of the shaft and the center of gravity of the head to be changed. In addition, bringing the position of the shaft 4 to the face side or the back side allows the progression to be changed.

In the above-described embodiment, the convex axis member 5 a has a quadrangular prism shape; however, it is also preferable that the convex axis member 5 a have a triangular prism shape. In the present invention, it is also preferable to use a convex axis member 5 a′″ that includes a plurality of convex threads 5 g provided on a lateral periphery of the convex axis member 5 a′″ as shown in a shaft case 5′″ shown in FIG. 14. The convex threads 5 g extend in a direction parallel to the axis center of the convex axis member 5 a′″. The other reference numerals in FIG. 14 are same as the reference numerals in the above-described embodiment.

In the present invention, it is also preferable to use a threaded ring 8′ that allows an insertion depth of a shaft case to be changed as shown in FIGS. 15 a and 15 b.

The threaded ring 8′ is provided with twelve concave threads 8 i similarly to the above-described threaded ring 8, and only four of the concave threads 8 i extend from the upper end to the lower end of the threaded ring 8′. Four of the other concave threads 8 i extend from the upper end to a depth of two thirds of the threaded ring 8′, and the other four concave threads 8 i extend from the upper end to a depth of one third of the threaded ring 8′.

The concave thread 8 i of which a ratio of the depth of the concave thread 8 i to the height of the threaded ring 8′ is one, the concave thread 8 i of which a ratio of the depth of the concave thread 8 i to the height of the threaded ring 8′ is one third, and the concave thread 8 i of which a ratio of the depth of the concave thread 8 i to the height of the threaded ring 8′ is two thirds are arranged in this order around an inner hole of the threaded ring 8′.

As shown in FIG. 16, when the convex axis member 5 a is put so as to strike thread lower ends 8 g of the concave threads 8 i having the depth ratio of two thirds, the entire length of the golf club is elongated by one third of the height of the threaded ring 8′. In this case, a spacer 31 that has a length of one third of the height of the threaded ring 8′ is sandwiched between the flange member 5 b and the upper end of the hosel column 3. When the convex axis member 5 a is put so as to strike thread lower ends 8 h of the concave threads 8 i having the depth ratio of one third, the entire length of the golf club is elongated by two thirds of the height of the threaded ring 8′, which is not shown in the drawings. In this case, a spacer that has a length of two thirds of the height of the threaded ring 8′ is sandwiched between the flange member 5 b and the upper end of the hosel column 3.

In this case, if the shaft axis center is coaxial with the hosel column axis center, changing the orientation of the shaft case 5 changes only the entire length of the golf club.

It is preferable that the above described ring, shaft case, hosel column, and bolt be made from metal, and in particular, it is preferable that the above described ring, shaft case, hosel column, and bolt be made from aluminum or titanium, or an alloy of aluminum or titanium. A shaft case that is made from an aluminum alloy to which alumite treatment is applied to increase the surface hardness so as to improve scratch resistance can be used as the shaft case; however, the present invention is not limited to this configuration. A hosel column that is made from pure titanium and produced by cutting work can be used as the hosel column; however, the present invention is not limited to this configuration. As one example of the present invention, the inner diameter of the upper end of the hosel column 3 is about 10.5 mm, the inner diameter of the lower end of the hosel column 3 is about 8.5 mm, and the diameter of a threaded shaft portion of the bolt 7 is about 4 to 5 mm; however, the present invention is not limited to these configurations.

The material from which the head is made is not limited particularly; however, in the case of a wood-type golf club head, the club can be made from, for example, a titanium alloy, an aluminum alloy, or a stainless steel. It is preferable that a titanium alloy used in the face be of low specific gravity such as a titanium alloy of Ti-6Al-1Fe, a titanium alloy of Ti-6Al-2Fe, and a titanium alloy of Ti-6Al-3 Fe. These titanium alloys have a specific gravity of about 4.4. Titanium alloys that have a specific gravity of 4.4 are as follows.

Ti-8Al-1V-1Mo (specific gravity 4.37)

Ti-7Al-2V (specific gravity 4.35)

Ti-7.5Al-2V (specific gravity 4.35)

Ti-8Al-1V (specific gravity 4.34)

Ti-8Al-2V (specific gravity 4.35)

Ti-8Al-1V-1Mo-0.15C (specific gravity 4.37)

Ti-6Al-1Fe (specific gravity 4.38)

It is to be noted that a grip that has a non-perfect round shape in cross section is sometimes used as a grip attached to the shaft 4. For example, a lower face of the outer periphery of the grip that is oriented to the ground at address sometimes has the shape expanding more than the other faces. In this case, when the orientation of the shaft case 5, 5A is changed, the expanding portion of the grip is not always oriented to the ground side. In order to solve this problem, it is preferable to use a grip that has a perfect round shape in cross section in the present invention.

In the above-described embodiment of the present invention, the golf club head is of a wood type; however, the present invention can be applied also to a utility-type golf club head that resembles the wood-type golf club head.

Next, a description of a method for producing the golf club will be provided.

In this production method, a head main body 10 in which a crown portion and a face portion are open as shown in FIGS. 6 and 10 is used. As shown in FIG. 10, the hosel column 3 is welded to the head main body 10, and the hosel column 3 and the head main body 10 have a monolithic construction. The hosel column 3 includes one or a plurality of holes 11 on the upper side of the dividing member 6. The holes 11 penetrate from the inner periphery to the outer periphery of the hosel column 3. In the present embodiment, a hole that faces the side of the face portion, and a hole that faces the toe side or the back side are provided as the holes 11.

The threaded ring 8 is attached to the top end of the shaft case 5, and the splines of the shaft case 5 are engaged with the splines of the threaded ring 8. The shaft case 5 that is attached with the threaded ring 8 is inserted into the hosel column 3, and the threaded ring 8 is brought into contact with the dividing member 6 as shown in FIG. 7. The holes 11 face the outer periphery of the threaded ring 8 in this state.

Then, the orientation (the phase of the circumferential direction) of the shaft case 5 is adjusted so that the mark “N” that is provided on the flange member 5 b of the shaft case 5 may face the toe side. After the adjustment, a welding operation is performed through the holes 11, and the hosel column 3 is welded to the threaded ring 8. A method for welding by melting both of the hosel column 3 and the threaded ring 8 preferably with the use of a TIG welding machine can be used in the welding operation; however, the present invention is not limited to this method. The arrows W in FIG. 7 indicate directions in which electrodes approach during this welding.

After the welding, the shaft case 5 is pulled out from the hosel column 3. The threaded ring 8 is left in the hosel column 3.

Then, the crown portion 1 b and the face portion 1 a that define sealing plates are welded to the crown portion and the face portion of the head main body 10, and a front edge of the crown portion 1 b is welded to an upper edge of the face portion 1 a as shown in FIG. 10. Then, fins are removed, and the head main body 10 is subjected to a finishing process such as painting. In this manner, the golf club head 1 where the threaded ring 8 is welded to the deepest recess of the hosel column 3 is obtained.

It is also preferable that a plate in which the crown portion 1 b and the face portion 1 a are of a monolithic construction be welded to the head main body 10. It is also preferable that a part or the entire of the crown be made from a CFRP.

While the head main body 10 including open portions at the crown portion and the face portion is used in FIGS. 6 and 7, it is also preferable to use a head main body including open portions at a face portion, and a sole portion or a part of a side portion at a heal side. When the hole 11 is provided only on the face side, a head main body including an open portion only at a face portion may be used; however, it is preferable to provide a plurality of holes 11 at intervals in a circumferential direction of the hosel column 3 so as to perform welding at a plurality of sites because fixing strength of the threaded ring 8 is increased.

While the threaded ring 8 is held by the shaft case 5 in welding the threaded ring 8 to the hosel column 3 in FIGS. 6 and 7, it is also preferable to use a jig that includes a top end portion having the same shape as the shaft case 5. It is preferable that the jig have a length larger than the length of the shaft case 5, and be provided with a mark same as the mark “N”. 

What is claimed is:
 1. A golf club comprising: a shaft; a head attached to a top end of the shaft; and a shaft case having an approximately cylindrical shape, bonded to the top end of the shaft, inserted into a hosel column of the head, and fixed to the hosel column, wherein: the hosel column includes a dividing member; a threaded ring including a plurality of threads provided on an inner periphery of an inner hole of the threaded ring is provided on an upper side of the dividing member, the threads extending in an axis center direction of the inner hole; the shaft case includes a convex axis member provided at a top end of the shaft case; the convex axis member has a prism shape, or includes convex threads that extend in an axis center direction on an outer periphery of the convex axis member; the convex axis member is inserted in the inner hole of the threaded ring, and any one of corner edges of the convex axis member and the convex threads connect with the threads of the threaded ring; and a bolt that is inserted into a bolt insertion hole provided to the dividing member from a sole side of the head is screwed into the shaft case, whereby the shaft case is fixed to the hosel column.
 2. The golf club according to claim 1, wherein: the convex axis member includes a female screw hole on a top end face of the convex axis member; and the bolt is screwed into the female screw hole.
 3. The golf club according to claim 1, wherein an axis center of the shaft is in a slanting direction with respect to an axis center of the cylindrical-shaped shaft case.
 4. The golf club according to claim 1, wherein the axis center of the shaft is parallel to an axis center of the cylindrical-shaped shaft case.
 5. The golf club according to claim 1, wherein the threads of the threaded ring include threads that have different depths from an upper end of the ring.
 6. The golf club according to claim 2, wherein an axis center of the shaft is in a slanting direction with respect to an axis center of the cylindrical-shaped shaft case.
 7. The golf club according to claim 2, wherein the axis center of the shaft is parallel to an axis center of the cylindrical-shaped shaft case.
 8. The golf club according to claim 2, wherein the threads of the threaded ring include threads that have different depths from an upper end of the ring. 